In 1977, the Food and Drug Administration (FDA) initiated proceedings to ban the subtherapeutic
uses of penicillin and tetracyclines in animal feed. Unfortunately, that important work was never
completed. Since 1977, new research further demonstrates that adding antibiotics to livestock feed
contributes to the growing problem of antibiotic resistance among foodborne and other pathogens.
Those resistant bacteria can be transferred to humans via contaminated food products or through
direct or indirect contact with animals.

While both agricultural and medical uses of antibiotics contribute to antibiotic resistance,
subtherapeutic use in animals is an important contributor to the problem.(1)

I. The FDA should ban subtherapeutic uses of antibiotics in livestock of those antibiotics that
may be used in (or that are related to those used in) human medicine.

The ban should include subtherapeutic uses of penicillin, tetracyclines, erythromycin, lincomycin,
tylosin, virginiamycin, and other antibiotics used in human medicine or related to those used in
human medicine for growth promotion and disease prevention.Subtherapeutic use of those
antibiotics in agriculture may jeopardize their effectiveness in treating human or animal diseases.

Banning subtherapeutic agricultural antibiotic uses can lead to a decrease in antibiotic resistance
among foodborne pathogens. For example, in Sweden, where glycopeptides have not been used as
growth promoters since the early 1980s, and were formally banned in 1986, vancomycin-resistant
enterococci are not found in isolates from pigs.(2) In contrast, in the Netherlands, where glycopeptides
only recently were banned, 39 percent of enterococci isolated from swine are vancomycin resistant.

II. The subtherapeutic use of antibiotics in livestock jeopardizes new human-use antibiotics
and jeopardizes human health.

A class of antibiotics called streptogramins is one of the last weapons against deadly antibiotic-resistant bloodstream infections caused by antibiotic-resistant enterococci. Although it has not yet
been approved for use in humans, the potential value of one streptogramin -- Synercid -- already has
been compromised because of subtherapeutic use of another antibiotic in the same class. That is
because resistance to one antibiotic can cause resistance to the entire family of antibiotics. Turkeys

that had been fed subtherapeutically another streptogramin, virginiamycin, harbor enterococci
bacteria that also are resistant to Synercid.(3) If people handle or consume turkey that is contaminated
with those streptogramin-resistant enterococci and become ill, Synercid, if and when it is approved

for human use, would be ineffective against that illness. In the U.S., Synercid-resistant bacteria have
not yet been found in humans. However, in Germany, a country in which Synercid is not yet used in
humans but in which virginiamycin is used subtherapeutically in livestock, Synercid-resistant
enterococci have been detected in humans.(4)

III. Leading health authorities around the world have called for banning subtherapeutic uses
of certain antibiotics in agriculture.

A number of authoritative organizations recognize that subtherapeutic antibiotic use in livestock
contributes to the development of antibiotic resistance and may pose a risk to human health.

The World Health Organization (WHO) recommends that the use of any antimicrobial for
growth promotion in animals should be banned if it is (1) used in human therapeutics or (2)
known to select for cross-resistance to antimicrobials used in human medicine.(5)

The U.S. Centers for Disease Control and Prevention (CDC) has advised that the U.S.
adopt the WHO position.(6)

The National Academy of Sciences recently concluded that agricultural uses of antibiotics
pose a risk to the public health.(7)

In addition, most developed nations, with the notable exception of the United States and Canada,
have banned the subtherapeutic use of penicillin and tetracycline. Sweden has banned the use of any
antibiotic. Denmark and Finland have banned several antibiotics for growth promotion. In
December 1998, the European Union banned the use of four antibiotics used in animal feed because
of concerns that those uses will undermine the effectiveness of antibiotics in human medicine (earlier
it had banned other antibiotics).

We urge you to take swift action to protect the effectiveness of antibiotics by limiting their
subtherapeutic use in agriculture. Without such action, we jeopardize one of the great advancements
in human and veterinary medicine.

Anne K. Vidaver, Ph.D.
Prof. and Head of Plant Pathology
University of Nebraska
Lincoln, NE

Ellen Wald, M.D.
Prof. of Pediatrics and Otolaryngology
Dept. of Allergy, Immunology and Infectious Diseases
University of Pittsburgh School of Medicine
Children's Hospital of Pittsburgh
Pittsburgh, PA

References1. The FDA and other agencies need to identify other agricultural and medical uses of antibiotics
that are problematic and also reduce those uses. See Center for Science in the Public Interest.
Protecting the Crown Jewels of Medicine: A Strategic Plan to Preserve the Effectiveness of
Antibiotics. Washington, DC: CSPI; 1998.